Since the development of integrated circuit technology, computers and computer storage devices have been made from integrated circuit ("IC") chips formed from wafers of semiconductor material. After a wafer is made, the chips are typically separated from each other by dicing the wafer. Thereafter, the individual chips are bonded to carriers of various types, interconnected by wires and packaged. Such "two-dimensional" packages of chips fail to optimize the number of circuits that might be fabricated in a given space, and also introduce undesirable signal delays, capacitance, and inductance as signals travel between chips.
Recently, electronic modules comprising three-dimensional arrays of chips have emerged as an important packaging approach. A typical three-dimensional dimensional electronic module consists of multiple integrated circuit chips adhesively secured together as a monolithic structure (a "stack"). A metallization pattern is often provided directly on one (or more) side surface(s) of the electronic module for interconnecting the chips in the stack and for electrical connection of the stack to circuitry external to the module. The metallization pattern can include both individual contacts and bus contacts.
One significant aspect in the fabrication of electronic modules is the electrical interconnection between surfaces of the module. For example, interconnection between the front face of a module (defined by a substantially planar main surface of an end semiconductor chip in the stack) is typically performed by use of a ceramic end cap. The front surface of the ceramic end cap contains metallized contacts for external connection. Electrically conductive vias originating from these contacts are etched completely through to the back surface of the cap. Back surface metallization then extends from the vias to edges of the end cap (corresponding to side surfaces of the module), connecting to side surface metallization. This interconnect scheme is complex and costly with respect to the fabrication of electronic modules.
Another significant consideration in the fabrication of electronic modules is the dissipation of electrostatic discharge ("ESD"). ESD in electronic modules produces high current densities, which cause local heating as the ESD passes through resistive epitaxial regions. This may cause destruction of circuits and wiring within the chips of the module.
Another significant problem in high density electronic modules is impedance mismatching, which results in ring-back. Specifically, in electronic modules, ring-back is a problem since the loading of signals is different depending on which chips in the module are accessed. Thus, significant additional componentry (such as resistors and capacitors) is needed external to electronic modules to account for various impedance mismatch problems. Further, decoupling of power supply voltages requires significant amounts of external capacitance.
The present invention is directed towards solving these problems.